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United States Patent |
6,029,300
|
Kawaguchi
,   et al.
|
February 29, 2000
|
Spin extractor
Abstract
In an inventive spin extractor, a speed controller applies a constant
voltage to a motor for starting a rotation of a drum. Since the torque on
the drum is constant, the drum rotates at a low speed when the laundry is
in the form of a large mass and the load on the drum is accordingly large.
Every time part or all of the laundry falls beyond the baffles provided on
the inner peripheral wall of the drum, the laundry is loosened and
scattered, so that the load on the drum decreases. When the laundry is
scattered adequately, the torque by the motor overcomes the load of the
laundry, and the drum speed rapidly rises. When the speed exceeds the
equilibrium speed where the centrifugal force acting on the laundry is
equal to gravity, the scattered laundry starts rotating in the state of
being pressed on the inner peripheral wall of the drum. When the drum
speed reaches a preset speed higher than the equilibrium speed, the speed
controller changes the speed control method to a phase control method for
maintaining the drum speed at an object speed. While the drum is rotating
at the object speed, the eccentric load detector detects the magnitude of
the eccentric load based on the periodical change in the motor current,
and a central controller determines whether the laundry is distributed
evenly on the inner peripheral wall of the drum.
Inventors:
|
Kawaguchi; Tomonari (Otsu, JP);
Suo; Kiyoyuki (Koka-gun, JP)
|
Assignee:
|
Sanyo Electric Co., Ltd. (Moriguchi, JP)
|
Appl. No.:
|
144087 |
Filed:
|
August 31, 1998 |
Foreign Application Priority Data
Current U.S. Class: |
8/159; 68/12.06; 68/12.14; 68/12.16 |
Intern'l Class: |
D06F 033/02 |
Field of Search: |
68/12.06,12.14,12.16
34/58,319
8/159
|
References Cited
U.S. Patent Documents
4853605 | Aug., 1989 | Matsuo et al. | 68/12.
|
5181398 | Jan., 1993 | Tanaka et al. | 68/12.
|
5301522 | Apr., 1994 | Ikemizu et al. | 68/12.
|
5325677 | Jul., 1994 | Payne et al. | 68/12.
|
5692313 | Dec., 1997 | Ikeda et al. | 68/12.
|
5765402 | Jun., 1998 | Ikeda et la. | 68/12.
|
5893280 | Apr., 1999 | Honda et al. | 68/12.
|
Foreign Patent Documents |
6-254294 | Sep., 1994 | JP.
| |
Primary Examiner: Coe; Philip R.
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
What is claimed is:
1. A spin extractor for extracting liquid from a laundry by rotating a
basket drum with the laundry loaded therein about a horizontal axis,
comprising:
a motor for rotating the basket drum;
a speed detector for detecting a speed of the motor; and
a speed controller for applying a constant voltage to the motor so that the
basket drum is rotated at a constant torque and the laundry loaded in the
basket drum is redistributed on an inner peripheral wall of the basket
drum in an initial stage of a liquid extracting operation until a speed of
the basket drum reaches a preset speed higher than an equilibrium speed at
which a centrifugal force acting on the laundry in the basket drum is
equal to gravity, and for controlling the motor so that an actual speed of
the motor detected by the speed detector is maintained at an object speed
after the speed of the basket drum reaches the preset speed.
2. A spin extractor for extracting liquid from a laundry by rotating a
basket drum with the laundry loaded therein about a horizontal axis,
comprising:
a motor for rotating the basket drum;
a speed detector for detecting a speed of the motor; and
a speed controller for controlling the speed of the motor by a process
comprising steps of:
applying a constant voltage to the motor so that the basket drum is rotated
at a constant torque in an initial stage of a liquid extracting operation
until a speed of the basket drum reaches a preset speed higher than an
equilibrium speed at which a centrifugal force acting on the laundry in
the basket drum is equal to gravity;
modifying the constant voltage when the constant torque is determined to be
out of an appropriate range with respect to a load on the basket drum due
to the laundry; and
controlling the motor so that an actual speed of the motor detected by the
speed detector is maintained at an object speed after the speed of the
basket drum reaches the preset speed.
3. The spin extractor according to claim 2, further comprising:
an eccentric load detector for detecting a magnitude of an eccentric load
due to an uneven distribution of the laundry based on a change in a
driving current supplied to the motor while the basket drum is rotated at
a speed higher than the equilibrium speed; and
an eccentric load determiner for determining whether the magnitude of the
eccentric load is greater than a preset value, and the speed controller is
constituted to stop the basket drum temporarily and then to start rotating
the basket drum again when the magnitude of the eccentric load is
determined to be greater than the preset value.
4. The spin extractor according to claim 3, further comprising a timer for
measuring a time period required for the speed of the basket drum to reach
a preset speed when a first constant voltage is applied to the motor by
the speed controller, and the speed controller is constituted to stop the
basket drum temporarily and to start rotating the basket drum again by
applying to the motor a second constant voltage lower than the first
constant voltage when the time period required thereby is shorter than a
preset time period.
5. The spin extractor according to claim 4, further comprising a lapse
timer for measuring a lapse of time from a start of an application of the
constant voltage to the motor, and the speed controller is constituted to
increase the voltage applied to the motor when the lapse of time reaches a
preset time period before the speed of the basket drum reaches a preset
speed.
6. The spin extractor according to claim 4, wherein the speed controller is
constituted to increase the voltage applied to the motor when the speed of
the motor detected by the speed detector is zero while the constant
voltage is applied to the motor.
7. The spin extractor according to claim 3, further comprising a lapse
timer for measuring a lapse of time from a start of an application of the
constant voltage to the motor, and the speed controller is constituted to
increase the voltage applied to the motor when the lapse of time reaches a
preset time period before the speed of the basket drum reaches a preset
speed.
8. The spin extractor according to claim 3, wherein the speed controller is
constituted to increase the voltage applied to the motor when the speed of
the motor detected by the speed detector is zero while the constant
voltage is applied to the motor.
9. The spin extractor according to claim 2, further comprising a timer for
measuring a time period required for the speed of the basket drum to reach
a preset speed when a first constant voltage is applied to the motor by
the speed controller, and the speed controller is constituted to stop the
basket drum temporarily and to start rotating the basket drum again by
applying to the motor a second constant voltage lower than the first
constant voltage when the time period required thereby is shorter than a
preset time period.
10. The spin extractor according to claim 9, further comprising a lapse
timer for measuring a lapse of time from a start of an application of the
constant voltage to the motor, and the speed controller is constituted to
increase the voltage applied to the motor when the lapse of time reaches a
preset time period before the speed of the basket drum reaches a preset
speed.
11. The spin extractor according to 9, wherein the speed controller is
constituted to increase the voltage applied to the motor when the speed of
the motor detected by the speed detector is zero while the constant
voltage is applied to the motor.
12. The spin extractor according to claim 2, further comprising a lapse
timer for measuring a lapse of time from a start of an application of the
constant voltage to the motor, and the speed controller is constituted to
increase the voltage applied to the motor when the lapse of time reaches a
preset time period before the speed of the basket drum reaches a preset
speed.
13. The spin extractor according to claim 12, wherein the speed controller
is constituted to increase the voltage applied to the motor when the speed
of the motor detected by the speed detector is zero while the constant
voltage is applied to the motor.
14. The spin extractor according to claim 2, wherein the speed controller
is constituted to increase the voltage applied to the motor when the speed
of the motor detected by the speed detector is zero while the constant
voltage is applied to the motor.
15. The spin extractor according to claim 2, wherein the speed controller
is constituted to control the speed of the motor by a phase control
process wherein a driving current supplied to the motor is an alternating
current cut off at a timing corresponding to a control angle within each
cycle of the alternating current and the speed of the motor is controlled
by changing the control angle, the process including steps of maintaining
the control angle until the speed of the basket drum reaches a preset
speed and determining the control angle based on the difference between
the actual speed and the object speed after the speed of the basket drum
reaches the preset speed.
16. The spin extractor according to claim 2, wherein the speed controller
is constituted to control the speed of the motor by a pulse width
modulation process wherein a driving current supplied to the motor is in a
form of a series of pulses each having a preset width and the speed of the
motor is controlled by changing the pulse width, the process including
steps of maintaining the pulse width until the speed of the basket drum
reaches a preset speed and determining the pulse width based on the
difference between the actual speed and the object speed after the speed
of the basket drum reaches the preset speed.
17. The spin extractor according to claim 2, comprising at least six
baffles provided on an inner peripheral wall of the basket drum at a
preset angular interval.
Description
The present invention relates to a spin extractor for extracting liquid
such as water or dry cleaning solvent from the laundry by rotating a
basket drum with the laundry loaded therein about a horizontal axis at
high speed. The spin extractor according to the present invention can be
used as a part of a washing machine whereby washing and extraction are
carried out continuously, or of a washing/drying machine whereby washing,
extraction and drying are carried out continuously.
BACKGROUND OF THE INVENTION
A so-called drum type or front loading type of spin extractor is
constituted so that the laundry is loaded in a basket drum having a
horizontal rotation axis, and that the drum is rotated about the axis at
high speed. One of the serious problems with this type of spin extractor
is that, when the drum is rotated at high speed with the laundry
distributed unevenly on its peripheral wall, abnormal vibration or noise
occurs due to the unbalance in mass distribution around the central axis
of the drum. For suppressing such vibration or noise, some of the
conventional washing/drying machines having the above type of spin
extractor have one or several weight pieces attached to an outer tub in
which the drum is mounted. This type of washing/drying machine, however,
is very heavy and large, so that it is difficult to move or transport it,
and its installation is limited.
Some proposals have been made addressing this kind of abnormal vibration or
noise of the drum type spin extractor. For example, the Publication No.
H6-254294 of the Japanese Unexamined Patent Application discloses a spin
extractor wherein the drum is rotated at low speeds for redistributing the
laundry on the inner peripheral wall of the drum before the drum is
rotated at a high speed for liquid extraction. In detail, the speed of the
drum is controlled by a two-stage balancing operation including steps of
rotating the drum at a first low speed for a short time and then rotating
the drum at a second low speed that is a little higher than the first low
speed and much lower than the high speed for extraction.
In addition, the above spin extractor has a vibration sensor on its base as
a means for detecting the eccentric load due to an uneven distribution of
the laundry in the drum. When the vibration sensor detects abnormal
vibration during the rotation of the drum at high speed, the drum speed is
reduced.
By the above-described method of controlling the drum speed, however, it is
not assured that the laundry is redistributed evenly on the inner
peripheral wall of the drum by a single cycle of the two-stage balancing
operation. Therefore, the balancing operation often becomes a trial and
error process including steps of rotating the drum at the low speeds for
correcting the balance, raising the drum speed to the high speed for
extraction and, responsive to a detection of abnormal vibration, reducing
the drum speed to rotate the drum at the low speeds again. If such a trial
and error process occurs, the time required for the extraction becomes
very long.
Besides, none of the conventionally proposed methods of correcting the
balance of the laundry effectively works when only one or a few large
articles, such as a bed sheet, are loaded in the drum, because this type
of article is hard to loosen when it retains water and forms a larger
mass.
SUMMARY OF THE INVENTION
For solving the above-described problems, the main object of the present
invention is to propose a spin extractor wherein the reliability of
obtaining an even distribution of the laundry is improved so that the
balance correction process is completed within a short time period.
Thus, the present invention proposes a spin extractor for extracting liquid
from a laundry by rotating a basket drum with the laundry located therein
about a horizontal axis, which includes a motor for rotating the basket
drum, a speed detector for detecting a speed of the motor, and a speed
controller for applying a constant voltage to the motor so that the basket
drum is rotated at a constant torque and the laundry loaded in the basket
drum is redistributed on an inner peripheral wall of the basket drum in an
initial stage of a liquid extracting operation until a speed of the basket
drum reaches a preset speed higher than an equilibrium speed at which a
centrifugal force acting on the laundry in the basket drum is equal to
gravity, and for controlling the motor so that an actual speed of the
motor detected by the speed detector is maintained at an object speed
after the speed of the basket drum reaches the present speed.
In the spin extractor according to the present invention, the speed
controller applies a constant voltage to the motor for starting the drum
to rotate with the laundry loaded therein. By this method, the drum speed
changes in the initial stage of the drum rotation. That is, when the
laundry is being lifted by one or more of baffles provided projecting on
the inner peripheral wall of the drum, the load on the drum is large, and
when all or part of the laundry falls beyond the baffle, the load on the
drum decreases rapidly. According to such a change in the load on the
drum, the drum speed also changes. Here, when the drum is rotated by an
appropriate constant torque, the drum speed does not exceed a specific
speed in the initial stage of the rotation where the laundry is in the
form of a large mass and the load of the laundry is accordingly large. As
the drum rotation proceeds, the laundry is gradually loosened and
redistributed on the inner peripheral wall of the drum, so that the load
on the drum decreases. When the load decreases to a certain level, the
torque generated by the motor overcomes the load of the laundry, at which
time the drum speed rapidly rises and then exceeds an equilibrium speed at
which the centrifugal force acting on the laundry is equal to gravity.
When drum speed reaches a preset object speed higher than the equilibrium
speed, the speed controller changes the speed control method to such a
method where the drum speed is maintained at the object speed.
By the above-described method of starting the drum rotation, the mass of
the laundry is loosened by the baffles, so that the laundry is easily
redistributed on the inner peripheral wall of the drum and the magnitude
of the eccentric load becomes smaller.
When the load on the motor changes, the driving current in the motor
contains an alternating torque component. So, when the laundry is unevenly
distributed on the inner peripheral wall of the drum, the driving current
of the motor changes according to the change in the load while the drum is
rotated with the laundry pressed on its inner peripheral wall by
centrifugal force.
Thus, in a preferable mode of the invention, the spin extractor further
includes: an eccentric load detector for detecting the magnitude of the
eccentric load due to the uneven distribution of the laundry based on the
change in the driving current supplied to the motor while the drum is
rotated at a speed higher than the equilibrium speed; and an eccentric
load determiner for determining whether the magnitude of the eccentric
load is greater than a preset value, and the speed controller is
constituted to stop the drum temporarily and then to start the drum
rotation again when the magnitude of the eccentric load is determined to
be greater than a preset value.
By this constitution, the determination result obtained based on the change
in the driving current supplied to the motor is used for estimating
whether abnormal vibration of the drum or the outer tub occurs during high
speed extraction. When the magnitude of the eccentric load is greater than
the preset value, the drum is stopped temporarily and then the drum
rotation is started again as described above, whereby the laundry is
redistributed.
In the spin extractor according to the present invention, when the voltage
applied to the motor is very high, or when the torque of the motor is very
large, the drum speed rises rapidly, so that the laundry starts rotating
in the state of being pressed on the inner peripheral wall of the drum by
centrifugal force before it is adequately redistributed.
Therefore, in a preferable mode of the invention, the spin extractor
further includes a timer for measuring a time period required for the drum
speed to reach a preset speed when a first constant voltage is applied to
the motor by the speed controller, and the speed controller is constituted
to stop the drum temporarily and to start the drum rotation again by
applying to the motor a constant voltage lower than the first constant
voltage when the time period required thereby is shorter than a preset
time period.
By this constitution, the time period measured by the timer is used for
determining whether the torque of the motor is greater than an appropriate
torque for the load of the laundry. When the time period measured by the
timer is shorter than the preset time period, the speed controller
determines that the torque of the motor is too large, and reduces the
voltage applied to the motor to reduce the torque. By this speed control,
the probability of the laundry's being redistributed in the drum becomes
higher in the re-started drum rotation.
When, on the other hand, the voltage applied to the motor for starting the
drum rotation is too low, or when the torque is too small, the drum does
not rotate at all, or the drum stops in the course of the rotation even if
it once starts rotating. Therefore, in a preferable mode of the invention,
the spin extractor includes a lapse timer for measuring the lapse of time
from the start of the application of the constant voltage to the motor,
and the speed controller is constituted to increase the voltage applied to
the motor when the lapse of time reaches a preset time period before the
drum speed reaches a preset speed.
In a still more preferable mode, the speed controller is constituted to
increase the voltage applied to the motor when the speed of the motor
detected by the speed detector is zero while the constant voltage is
applied to the motor.
In another mode of the present invention, the speed controller is
constituted to control the speed of the motor by a phase control process
wherein the driving current supplied to the motor is an alternating
current cut off at a timing (or a phase angle, which is referred to as "a
control angle" hereinafter) within each cycle of the alternating current,
and the speed of the motor is controlled by changing the control angle.
The process includes steps of maintaining the control angle until a preset
speed is reached and determining the control angle based on the difference
between the actual speed and an object speed after the preset speed is
reached.
In still another mode of the present invention, the speed controller is
constituted to control the speed of the motor by a pulse width modulation
process wherein the driving current supplied to the motor is in a form of
a series of pulses each having a preset duration (pulse width), and the
speed of the motor is controlled by changing the pulse width. The process
includes steps of maintaining the pulse width until a preset speed is
reached and determining the pulse width based on the difference between
the actual speed and an object speed after the preset speed is reached.
In the spin extractor according to the present invention, the baffles play
an important role in the process of redistributing the laundry. So, it is
preferable to provide an adequate number of baffles on the inner
peripheral wall of the drum to improve the redistributing efficiency. For
example, it is recommended to provide at least six baffles on the inner
peripheral wall of the drum at every preset angular interval.
As explained above, in the spin extractor according to the present
invention, at first the motor generates a constant torque while the drum
speed increases from zero to a preset speed, and after the preset speed is
reached, the motor is driven so that the actual speed of the motor
detected by the speed detector is maintained at the object speed. In the
initial stage of the drum rotation, the drum speed changes according to
the change in the load on the drum that occurs when the laundry is moved
in the drum by baffles as described above. When the laundry is scattered
beyond the baffles and the load on the drum becomes adequately small, the
speed of the drum increases rapidly, whereafter the drum starts rotating
with the laundry pressed on its inner peripheral wall by centrifugal
force. Thus redistributing the laundry on the inner peripheral wall of the
drum, the load balance of the drum is corrected in a short time, and the
high speed extraction is started promptly. Accordingly, the time required
for extraction, and further the time required for the whole process
including washing and extraction, are shortened.
In the inventive spin extractor, the laundry rolls over the baffles at a
relatively low speed in the initial stage of the drum rotation. So, when
one or few of large laundry articles, such as a bed sheet, are loaded in
the drum in the form of a large mass with water retained therein, the
laundry is gradually loosened and expanded every time it rolls over each
of the baffles, whereby the balance is corrected adequately so that the
magnitude of the eccentric load becomes adequately small.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a drum type washing machine including a spin
extractor embodying the present invention, wherein a side panel is
removed;
FIG. 2 is a rear view showing the main part of the machine, where a rear
cover is removed;
FIG. 3 is a block diagram showing the electrical system of the washing
machine;
FIGS. 4A-4C are graphs showing an example of wave form for explaining the
process of controlling the speed of the motor in the washing machine;
FIG. 5 is a graph showing an example of wave form of the motor current
changing under the influence of the eccentric load;
FIGS. 6 and 7 are flow charts showing the process of starting the drum
rotation in the extracting operation; and
FIGS. 8A-8E, 9A-9D are illustrations showing the movement of the laundry in
the drum.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
A drum type washing machine including a spin extractor embodying the
present invention is explained referring to FIGS. 1-9. First, the whole
structure of the washing machine is described referring to FIGS. 1 and 2.
A body case is built up by a frame 1, a top plate 2, a front panel 3, a
rear cover 4 and a base 5. In the body case, an outer tub 6 having a front
opening is hung by springs 7 and sustained by dampers 8 for absorbing
vibration. The front panel 3 has a door 9 for closing the front opening of
the outer tub 6. The door 9 is opened when the user throws the laundry
through the front opening of the outer tub 6 into a drum 10 provided in
the outer tub 6. The drum 10 has a shaft holder 11 on its rear part, to
which a main shaft 12 is securely attached. The main shaft 12 is born by a
bearing structure 13 provided at the rear part of the outer tub 6. The
bearing structure 13 includes a roller bearing 14 for rotatably holding
the main shaft 12. An end of the main shaft 12 is protruding out from the
rear part of the outer tub 6, and a large pulley 15 is fixed to the end. A
motor 16 is disposed under the outer tub 6, and a small pulley 17 is fixed
to the rotation axis of the motor 16. The small pulley 17 is drivingly
connected with the large pulley 15 by a V-belt 18.
Water supplied from an outside source, such as a water tap, is introduced
through a water supply hose 19 into a water supply unit 20. Though not
shown, the water supply unit 20 has a water passage, a valve disposed in
the water passage, and a detergent dispenser also disposed in the water
passage. When water is introduced in the water passage, the detergent
contained in the detergent dispenser eludes into the water, thus producing
detergent water, and the detergent water is injected into the outer tub 6.
The drum 10 has a number of perforations 10a formed in its peripheral
wall, through which the water injected into the outer tub 6 enters the
drum 10. The perforations 10a also function as water outlets during the
extraction. That is, water extracted from the laundry during the
extraction is centrifugally drained from the perforations 10a to the
outside of the drum 10. On the inner peripheral wall of the drum 10 are
disposed baffles 10b at every preset angular interval for lifting the
laundry. The washing machine of the present embodiment is designed to have
six baffles 10b, as shown in FIG. 8. It should be noted that the number of
baffles may be other than six, preferably more than six. A drainage pump
21 is provided for draining water gathered at the bottom of the outer tub
6. The water drained from the outer tub 6 passes a lint filter 22, which
can be taken out from the front end, and is discharged from a drainage
hose 23 to the outside.
The configuration and operation of the electrical system of the main part
of the above washing machine is described referring to FIG. 3. A control
unit 30 consisting mainly of one or several micro-computers functionally
includes a central controller 31, a phase controller 32, an eccentric load
detector 33 and other functional units (not shown). The central controller
31 includes a memory (not shown) wherein operation programs for carrying
out a washing process (including extracting operation) are stored
beforehand. During the extracting operation, the central controller 31
receives signals or information relating to the magnitude and position of
the eccentric load from the eccentric load detector 33, and processes the
information by a method explained later to calculate an object speed Np
corresponding to a desirable drum speed. The object speed Np is sent to
the phase controller 32.
A motor driving unit 40 includes an alternating current source (AC) 41 and
a switch (SW) 42. The motor driving unit 40 and the phase controller 32
function as a speed controller for controlling the speed of the motor 16.
The motor 16 is equipped with a speed detector 51 consisting of a pulse
generator and other elements. The speed detector 51 generates pulse
signals indicative of the actual speed Nr of the motor 16. The pulse
signals are sent to the phase controller 32 for a feedback control
explained later.
A current detector 50 detects a driving current (motor current) supplied
from the motor driving unit 40 to the motor 16, converts the current to a
voltage, and sends the voltage signal to the eccentric load detector 33.
FIG. 5 is a graph showing an example of waveform of the torque component
in the motor current, changing according to the lapse of time. In FIG. 5,
rotation markers are marker signals generated by a rotation sensor 52
provided to the drum 10, each rotation marker indicative of one rotation
cycle of the drum 10. When an eccentric load exists in the drum 10, the
torque component in the motor current periodically changes, as shown in
FIG. 5, depending on the eccentric load. Since the change in the motor
current corresponds to the change in the load torque, the maximum value
Vmax of the torque component appears when the load torque is maximized in
each rotation of the drum 10. The difference between the maximum value
Vmax and the minimum value Vmin (amplitude of the current change)
corresponds to the magnitude of the eccentric load. The relation between
the amplitude of current change and the magnitude of the eccentric load is
investigated beforehand, and the relation data is stored in the memory of
the central controller 31 in the form of a table, for example. The
relation table is used for calculating the magnitude of the eccentric load
from an amplitude of current change.
In detail, the calculation is performed as follows. When an electric
current having a waveform as shown in FIG. 5 is given, the eccentric load
detector 33 detects the maximum value Vmax and the minimum value Vmin of
the electric current for each interval of the rotation markers, i.e. for
each rotation of the drum 10, and calculates the difference between the
two values. The magnitude of the eccentric load is obtained from the
differential value (amplitude of the current change) based on the relation
table. Also, the position of the eccentric load on the inner peripheral
wall of the drum 10 may be detected based on the timing of detecting the
maximum value Vmax. The timing is represented by a delay time or angle
from the nearest of the preceding rotation markers, for example.
The process of controlling the speed of the motor 16 is described in
detail, referring to FIG. 4 and focusing on the operation of the phase
controller 32 and the motor driving unit 40. The phase controller 32
determines a control angle .alpha.[deg] based on the difference between
the object speed Np and the actual speed Nr, and sends a signal indicative
of the angle .alpha. to the switch 42. The switch 42 consists of a gate
control type of semiconductor switch, such as a triac, and other elements,
for example. The AC source 41 supplies to the switch 42 a sine wave
alternating current of a single phase as shown in FIG. 4A, and the switch
42 turns the alternating current ON and OFF according to the control angle
.alpha.. In detail, a pulse signal is generated at a position delayed by
the control angle .alpha. from each base position corresponding to phase
angle 0[deg], as shown in FIG. 4B. The electric current is turned OFF
during the angular interval from 0 to .alpha.[deg], and is turned ON
during the angular interval from .alpha. to 180[deg]. As a result, a
series of current pulses are supplied intermittently to the motor 16 as
the driving current, as indicated by the shaded areas in FIG. 4C. The
driving current (or driving power) supplied to the motor 16 increases when
the phase controller 32 sets the control angle .alpha. smaller, and vice
versa.
The process of controlling the drum speed in the initial stage of the
extracting operation by the above washing machine is described referring
to the flow charts of FIGS. 6 and 7. In the following description, values
of various parameters are calculated under the condition that the diameter
of the drum 10 is 470[mm]. It should be understood that the values are
just illustrative, and the parameters may take different values when the
diameter of the drum 10 is different.
After the completion of washing or rinsing, the laundry in the drum 10 are
crammed and piled at the bottom of the drum 10. Therefore, the central
controller 31 sends a loosening operation start signal to the phase
controller 32 for starting a loosening operation (Step S10). In the
loosening operation, the drum 10 is rotated back and forth at a speed of,
for example, about 55[rpm]. By this operation, the laundry articles
entangled together are loosened, so that it is now easier for the articles
to separate.
After carrying out the loosening operation for a preset time, the driving
current to the motor 16 is turned off for a preset time of, for example,
8[sec] (Step S11). The time is preset long enough for the drum 10 to stop
completely during the time. After that, an initial phase angle IK is
determined as follows. First, the central controller 31 sets the control
angle .alpha. at 110[deg], and sends a signal indicative of the angle
.alpha. to the phase controller 32, whereby a voltage corresponding to the
control angle .alpha. is applied to the motor 16 (Step S12). The control
angle .alpha. in Step S12 is preset to correspond to a low voltage for
generating such a small torque that can rotate the drum 10 only when the
amount of the laundry loaded in the drum 10 is very small.
After that, based on the output of the speed detector 51, the central
controller 31 determines whether a pulse signal from the speed detector 51
is detected within 0.5[sec] after starting the application of the voltage
to the motor 16 (Step S13). When no pulse signal is detected in Step S13,
it means that the motor 16 is not rotating or that the torque of the motor
16 is not large enough to overcome the load of the laundry in the drum 10.
Thus, when no pulse signal is detected, the control angle .alpha. is
reduced by, for example, 50[.mu.sec] or about 1[deg] in angle (Step S14),
whereby the torque of the motor 16 also increases since the voltage
applied to the motor 16 increases. Thus, while the determination result in
Step S13 is "NO", the modification of the control angle .alpha. in Step
S14 is repeated, and the torque of the motor 16 increases incrementally.
When it is determined in Step S13 that the pulse signal is detected within
0.5[sec], the central controller 31 starts measuring the lapse of time
(t1) by a timer (Step S15). After t1 reaches a preset time period, the
central controller 31 determines whether the speed of the drum 10 is
higher than 100[rpm] (Step S16). By the washing machine of the present
embodiment, the centrifugal force acting on the laundry is balanced with
gravity when the speed of the drum 10 is within the range of 70 to
80[rpm]. Accordingly, when the drum speed is 100[rpm], the laundry is
pressed on the inner peripheral wall of the drum 10 and rotates with the
drum.
In Step S16, when it is determined that the speed of the drum 10 is lower
than 100[rpm], the central controller 31 determines whether a pulse signal
from the speed detector 51 is detected within 0.5[sec] (Step S17). When it
is determined in Step S17 that no pulse signal is detected for more than
0.5[sec], it is concluded that the drum 10 has stopped in the midrotation,
so that the operation proceeds to Step S14 where the control angle .alpha.
is further reduced by 50[.mu.sec]. When, on the other hand, it is
determined in Step S17 that a pulse signal is detected within 0.5[sec],
the operation proceeds to Step S18 where the central controller 31
determines whether t1 is greater than 6[sec]. When t1 exceeds 6[sec]
before the speed of the drum 10 attains 100[rpm], it is concluded that the
torque is not adequately large, so that the operation proceeds to Step S14
where the control angle .alpha. is further reduced by 50[.mu.sec].
When it is determined in Step S16 that the speed of the drum 10 is higher
than 100[rpm], the control angle .alpha. at the moment is defined as the
initial phase angle IK (Step S19). After that, the method of controlling
the speed of the motor 16 is changed to a phase control method. That is,
the central controller 31 gives an object speed Np of the motor 16 to the
phase controller 32, and the phase controller 32 determines the control
angle .alpha. based on the difference between the actual speed Nr and the
object speed Np. Then, by the phase control method, the speed of the drum
10 is raised to 130[rpm] (Step S20). The laundry is pressed on the inner
peripheral wall of the drum 10 and rotates with the drum 10 at that speed
because the centrifugal force is greater than gravity. The eccentric load
detector 33 detects the eccentric load based on the periodical change in
the driving current supplied to the motor 16, as described above (Step
S21).
After obtaining the magnitude and position of the eccentric load in Step
S21, the central controller 31 determines whether the magnitude of the
eccentric load is smaller than a preset value (Step S22). When it is
determined in Step S22 that the magnitude of the eccentric load is smaller
than the preset value, it is concluded that little or no vibration is
expected to occur during the extracting operation with the current loading
condition. Thus, the operation proceeds to Step S23 where the speed of the
drum 10 is raised to a preset high speed of, for example, 1000[rpm].
When, on the other hand, it is determined in Step S22 that the magnitude of
the eccentric load is greater than the preset value, a scattering
operation is carried out as follows. First, in Step S24, a loosening
operation is carried out, as in Step S10. After that, the driving current
to the motor 16 is turned off for a preset time of 8[sec] for stopping the
drum 10 completely (Step S25). The phase controller 32 sends the initial
phase angle IK determined beforehand to the motor driving unit 40 as the
control angle .alpha., whereby a voltage corresponding to the phase angle
IK is applied to the motor 16 (Step S26). At the same time, the central
controller 31 start measuring the lapse of time (t2) by the timer (Step
S27).
The central controller 31 determines whether a pulse signal from the speed
detector 51 is detected within 1.5[sec] after the start of the time
measurement (Step S28). When no pulse signal is detected, it is concluded
that the motor 16 has stopped because the torque is not adequately large.
Thus, the phase controller 32 reduces the control angle .alpha. by
50[.mu.sec] (Step S30), and the initial phase angle IK is set at the new
control angle .alpha. (Step S40). With the modified value of IK, the
process of Steps S24 through S28 is carried out again. This time, the
torque of the motor 16 is greater because the voltage applied to the motor
16 is higher.
In Step S28, when the pulse signal is detected within 1.5[sec], it is
concluded that the motor 16 has not stopped. So, the central controller 31
determines whether the speed of the drum 10 is higher than 100[rpm] (Step
S29). In Step S29, when the speed is not higher than 100[rpm], it is
determined whether the lapse of time t2 is greater than 7[sec] (Step S31).
When t2 is not greater than 7[sec], the operation returns to Step S28.
When t2 exceeds 7[sec] before the speed of the drum 10 attains 100[rpm],
it is concluded that the torque is not adequately large, so that the
operation proceeds to Step 30 where the control angle .alpha. is further
reduced by 50[.mu.sec]. For example, when the laundry happens to be
gathering at one of the baffles 10b after the start of the drum rotation,
the time t2 may exceed 7[sec] before the speed of the drum 10 reaches
100[rpm] because it is difficult to dislodge the laundry beyond the baffle
10b.
In Step S29, the measurement of the time t2 is terminated when it is
determined that the speed of the drum 10 is greater than 100[rpm], and the
value t2 at the moment is stored in the memory (RAM) of the central
controller 31 (Step S32). After that, the method of controlling the speed
of the motor 16 is changed to the phase control method, and the speed is
raised to 130[rpm], as in Step S20 (Step S33). After the speed attains
130[rpm], the eccentric load detector 33 detects the eccentric load, as in
Step S21 (Step S34).
In Step S35, the central controller 31 determines whether the magnitude of
the eccentric load is smaller than the preset value. When the magnitude of
the eccentric load is smaller than the preset value, the speed of the drum
10 is raised to the high speed for extraction (Step S23). When, on the
other hand, the magnitude of the eccentric load is greater than the preset
value in Step S35, the central controller 31 reads out the time t2 from
the RAM and determines whether t2 is smaller than 2.5[sec] (Step S36).
When t2 is smaller than 2.5[sec], it is concluded that the torque for
rotating the drum 10 is so large that the laundry cannot be scattered in a
manner described later. Therefore, the control angle .alpha. is increased
by 250[.mu.sec] (Step S37), and the operation proceeds to Step S40.
In Step S36, when t2 is greater than 2.5[sec], it is determined whether t2
is smaller than 3[sec] (Step S38). When t2 is within the range of 2.5 to
3[sec], it is concluded that the torque for rotating the drum 10 is a
little too large for the laundry to be adequately scattered.
Therefore, the control angle .alpha. is increased by 50[.mu.sec] (Step
S39), and the operation proceeds to Step S40. In Step S38, when t2 is
greater than 3[sec], the operation proceeds to Step S40 without modifying
the control angle .alpha..
By the above speed control method, the drum 10 starts rotating at a
moderate rate of acceleration, and the speed of the drum 10 reaches
100[rpm] within several seconds. FIGS. 8A-8E and 9A-9D illustrate how the
laundry moves in the drum 10 while the speed of the drum 10 is controlled
as described above. FIGS. 8A-8E show the case where a plurality of small
laundry articles are loaded in the drum 10, and FIGS. 9A-9D show the case
where a single piece of large laundry article, such as a bed sheet, is
loaded in the drum 10.
Referring to FIGS. 8A-8E, at first the laundry articles lie at the bottom
of the drum 10 as shown in FIG. 8A. When the drum 10 starts rotating, the
articles are lifted by the baffles 10b as shown in FIG. 8B. Then, some of
the articles fall beyond the baffles 10b onto the bottom, as shown in FIG.
8C. Such a process is repeated while the drum 10 is rotating. When most of
the articles are being lifted by the same baffle 10b as shown in FIG. 8B,
the gravity acting on the articles works as a load against the rotation of
the drum 10, so that a large torque is necessary to maintain the rotation
of the drum 10. When, on the other hand, the drum 10 further rotates and
some of the laundry falls off (or beyond) the baffle 10b as shown in FIG.
8C, the load caused by gravity decreases rapidly, and the torque necessary
to maintain the rotation of the drum 10 becomes smaller.
Accordingly, when a constant voltage is applied to the motor 16 in the
initial stage of the drum rotation, the drum 10 rotates at a low speed
when the load is large as shown in FIG. 8A, and then the speed increases
rapidly when the load becomes smaller as the laundry is loosened as shown
in FIG. 8C. The speed of the drum 10 increases gradually as the laundry
articles are scattered on the inner peripheral wall of the drum 10.
When the constant voltage applied to the motor 16 in the initial stage is
determined appropriately, the mass of the laundry is loosened and the
laundry articles are scattered on the inner peripheral wall of the drum 10
every time part of the laundry falls beyond the baffles 10b in the course
of the rotation. When the load becomes adequately small, the speed of the
drum 10 rapidly increases and reaches a speed where the centrifugal force
acting on the laundry is greater than gravity. Thus, the scattered laundry
is pressed on the inner peripheral wall of the drum 10 and rotates with
the drum 10 as shown in FIG. 8E. When, on the other hand, the constant
voltage applied to the motor 16 in the initial stage is too high, the
speed of the drum 10 increases so rapidly that the drum 10 starts rotating
with the laundry pressed on its inner peripheral wall as shown in FIG. 8B
before the laundry is loosened adequately.
Hence, in the above embodiment, at first a control angle .alpha. that
determines the initial voltage to be applied to the motor 16 (i.e. the
initial phase angle IK) is determined by Steps S13 through S19, and the
control angle .alpha. is modified by Step S26 and the subsequent steps
taking account of the result of a test where the motor 16 is actually
energized with the control angle .alpha.. As a result of this modification
process, an appropriate voltage to be applied to the motor 16 is
determined. With this voltage being applied to the motor 16, the laundry
is scattered properly in the drum 10 in the initial stage of the drum
rotation.
In the case where the laundry consists of a single piece of large article,
at first the article lies at the bottom of the drum 10 as shown in FIG.
9A. As the rotation of the drum 10 proceeds, the article is gradually
loosened every time it rolls beyond the baffle 10b, as shown in FIGS. 9B
and 9C. When the load becomes adequately small, the speed of the drum 10
increases rapidly, so that the drum 10 starts rotating with the laundry
spread out and pressed on the inner peripheral wall of the drum 10 by
centrifugal force, as shown in FIG. 9D. Thus, the load balance around the
rotation axis of the drum 10 is corrected, and the eccentric load is very
small.
It should be noted that the above embodiment is a mere example, and the
present invention is applicable not only to a drum type washing machine
using water, but also to a dry cleaner using a petroleum detergent or
other liquid material, for example.
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